Starship Shielding
From Halopedia, the Halo wiki
Summary
The only known starships to have shields are Covenant ships.
All Covenant vessels are protected by a highly resistant energy shield that can recharge over time. Covenant Starships shield's are a light-gray color. The shields can take a vast amount of punishment, and can recharge very quickly. They can absorb anything including hundreds of Archer Missiles and even a Shiva nuclear missile. The only UNSC weapon capable of penetrating a Starship's Shields is the MAC cannon. Even then, it takes usually three rounds to drop its shields. However, a Super-MAC round can easily punch a hole through a Covenant starship's shield. The only flaw of Covenant Starship shields is that when the vessel fires its Plasma weapons, the ship needs to drop a section of its shields for a few seconds in order to let the plasma bolt out. This leaves it vulnerable to attack at that point. Additionally, when a Covenant ship unloads troops and supplies, it must lower its shields to let dropships out.
Plasma, and energy weapons on the other hand can easily disable the shields. It must be noted that the size, and class of the vessel determines the strength of the shields. Also, even though the shield can absorb a direct nuclear missile, if it detonates "inside" the shield, the blast will be magnified. It has been observed exploding inside the shield, and destroying the ship before the shields collapse. It is theorized the small area the blast explodes in multiplies it several hundred times.
